1. Field of the Invention
The present invention relates to methodologies and structure to support Circuit-Mode Data Services Over the A-interface.
2. Description of Related Art
The A-interface is an interface between the Base Station (BS) and the Mobile Switching Center (MSC) as defined in TIA/EIA/IS-634A. The first public disclosure of the invention was in the form of a contribution to TIA/TR45.4 standard meeting held on May 20-24, 1996; the contribution was subsequently adopted as part of a new TIA/EIA/IS-634A A-interface standard.
Circuit-mode data includes Asynchronous Data and G3 Fax as defined in TIA/EIA/IS-707 and TIA/EIA/IS-135. However, circuit-mode data support over A-interface was not defined in IS-634A prior to submission of the contribution by the inventors.
For Code Division Multiple Access (CDMA) circuit mode data services, a Radio Link Protocol (RLP, as defined in TIA/EIA/IS-707) replaces the vocoder used for voice services, to reliably transport data over the CDMA physical layer. For Time Division Multiple Access (TDMA) circuit mode data services, a Radio Link Protocol (RLP1, as defined in TIA/EIA/IS-130) replaces the vocoder used for voice services, to reliably transport data over the TDMA physical layer.
As in one particular case of the vocoder, RLP resides on the BS for CDMA. In the case of TDMA, RLP1 resides on the Interworking Function (IWF). For an architecture with IWF connected to the MSC, a link layer is between BS and MSC carrying, in the case of CDMA, data between RLP and upper-layers protocol instead of using pulse code modulation (PCM) and, in the case of TDMA, RLP1 data frame instead of using PCM.
This architecture, therefore, necessitates a new procedure and protocol to adapt the low speed mobile data over higher speed digital channels, i.e. DS0S. Each DS0 is a channel of 64 kilobits per second and supports 1 voice call but data is not transmitted across. There are 24 DS0s in a trunk line T1.
For an understanding of protocols and their terminology, refer to Intersystem Link PN-3660 Protocol, V & V Text Rev. 1.3, Copyright 1996 Telecommunications Industry Association. PN-3660 was developed by TR45.2, the TIA Intersystem Operations Subcommittee, and has been accepted into standard TIA/EIA/IS-728.
Terminology understood in the standards and as used in this application include the following:
A Base Station to Mobile Switching Center interface ADS Asynchronous Data Service BS Base Station CDMA Code Division Multiple Access E Mobile Switching Center to Mobile Switching Center interface GSM Global System for Mobility ISLP Intersystem Link Protocol IWF Interworking Function L Interworking Function to Mobile Switching Center Interface MS Mobile Station (may include a Mobile Termination) MSC Mobile Switching Center PCM Pulse Code Modulation RLP Radio Link Protocol SDU Service Data Unit TDMA Time Division Multiple Access U.sub.m Air interface between BS and MS
Conventional telecommunications standards include:
1. TIA/EIA/PN-3770 Intersystem Operations Support for Data Services, Telecommunications Industries Association, 1997.
2. TIA/EIA/IS-99. Data Services Option Standard for Wideband Spread Spectrum Digital Cellular System. Telecommunications Industry Association, 1995.
3. TIA/EIA/IS-130. 800 MHz Cellular Systems--TDMA Radio Interface--Radio Link Protocol 1. Telecommunications Industry Association, 1995.
4. TIA/EIA/IS-135. 800 MHz Cellular Systems--TDMA Services--Async Data and Fax. Telecommunications Industry Association, 1995.
5. TIA/EIA/IS-707. Data Service Options Support of 14.4 kbit/s Data Rate for Wideband Spread Spectrum Systems. Telecommunications Industry Association, 199x.
6. TIA/EIA/IS-41-C. Cellular Radio Telecommunication Inter System Operations, Telecommunications Industry Association, 199x.
7. TIA/EIA/IS-634-A. MSC-BS Interfaces for Public Mobile and Personal Communication Systems, Telecommunications Industry Association, 1997.